Gender difference in smoking effects on adult pulmonary function

Abstract

Data on 1,618 male and 1,669 female adults aged 40-69 yrs, from China in the Beijing Respiratory Health Study, were analysed to investigate the gender differences in effects of smoking on pulmonary function. Smoking was characterized by total smoking-years, smoking status (former, transitional and constant), smoking type (cigarette, cigar and others). The effects of smoking on height-standardized forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were assessed by multiple regressions adjusting for age, education level, use of an indoor coal stove for heating, passive smoking, occupational dust and gas/fume exposure, and residence. Prediction equations were derived from nonsmoking asymptomatic subjects. As compared to women, men had a much higher smoking prevalence (78 vs 35%) but a lower quitting rate (14 vs 23%). Female lifetime nonsmokers had greater mean percentage predicted lung function values than male lifetime nonsmokers, whilst female cigarette smokers had lower values than their male counterparts. In both sexes, the highest mean percentage predicted lung function values were found in lifetime nonsmokers, whilst the lowest values were found among former smokers, the second lowest among transitional smokers, and constant smokers actually had greater values than both former and transitional smokers. These findings were confirmed by sex-specific regression analyses. A global test on the interactions between smoking and sex was highly significant. This study suggests that adverse smoking effects on pulmonary function were greater in women than in men. This gender difference in the effects of smoking on pulmonary function may be related, in part, to the gender difference in smoking prevalence in the population, creating an incomparability of the lifetime nonsmoker reference group between the two sexes. The inverse gradient of lung functions for former, transitional and constant smokers may be explained by the 'healthy smoker effect'.